The donationware model works for me and DF, but I don't think it would work that well for a larger production. Because of the uncertainty associated with relying on payments after the fact, I think even the high budget game producers that you do like (if any!) would completely desert the market (e.g. for one of the other options I listed above) rather than risk their time and money.
The standard model of distribution is perhaps more, but not ultimately certain. Game's financial success isn't certain. A programmer will have his salary, but the company can bankrupt if several games sell worse then they expected.
You have the point that there would be much harder for big companies to make money... but it could also mean they are just too big to be competitive on such terms. Your model of development have a big advantage: it doesn't rely on people's honesty or the copyright law. They pay because they want to see the game improved. I wouldn't call it an uncertain revenue, only if the game is developed and people still want to see it developed.
Dwarf Fortress is an unique case: it's hard to encourage somebody to play it (because of graphics and interface), but if someone manages to overcome these difficulties, he will most propably stay. The source of income is small but as steady as it could be. I don't know if any mainstream game could achieve that. The propability would propably grow with the game's originality and susceptibility to improvements.
Spore could propably manage to earn money this way,
FPS Shooter #002BF5 wouldn't even live to its second release.